1. Field of the Invention
The present invention relates to mobile networks and, more particularly, the present invention relates to a technique for setting up multimedia calls in mobile networks using an IP (Internet Protocol) transport mechanism.
2. Description of the Related Art
In general, packet switched wireless networks provide communications for mobile terminals with no physical connection required for network access. The General Packet Radio Service (GPRS) in the Global System for Mobile Communications (GSM) and the Universal Mobile Terrestrial System (UMTS) have both been developed to provide wireless communications networks with a packet switched side, as well as a circuit switched side.
The specification for a UMTS network with further improvements has been released by the 3rd General Partnership Project. The UMTS specification provides that a network subscriber can have one or more packet data protocol (PDP) addresses. Each PDP address is described by one or more PDP contexts in the Mobile Station (MS), the Service GPRS Service Node (SGSN), and the Gateway GPRS Service Node (GGSN). A GGSN is a gateway to an external network. Each PDP context may have routing and mapping information for directing the transfer of data to and from its associated PDP address and a traffic flow template (TFT) for reviewing the transferred data.
Each PDP context can be selectively and independently activated, modified, and deactivated. The activation state of a PDP context indicates whether data transfer is enabled for a corresponding PDP address and TFT. If all PDP contexts associated with the same PDP address are inactive or deactivated, all data transfer for that PDP address is disabled. All PDP contexts of a subscriber are associated with the same Mobility Management (MM) context for the International Mobile Subscriber Identity (IMSI) of that subscriber. Setting up a PDP context means setting up a communications channel.
An example of the PDP context activation procedure is shown in FIG. 2. The activate PDP context request message sent in step 1 includes a number of parameters. The parameters include a PDP address and an Access Point Name (APN). The PDP address is used to indicate whether a static PDP or dynamic PDP address is required. The APN is a logical name referring to the Gateway GPSR Support Node (GGSN) to be used. In step 3, the SGSN sends a Radio Access Bearer (RAB) setup message to the UMTS Terrestrial Radio Access Network (UTRAN). In step 4, the SGSN sends a Create PDP Context Request message to the affected GGSN. The GGSN decides whether to accept or reject the request. If it accepts the request, it modifies its PDP context table and returns a Create PDP Context Response message. The SGSN then sends an activate PDP Context Accept message to the MS in step 5.
In spite of the numerous details provided in the aforementioned Protocol, many features associated with IP mobile networks have not been addressed. Specifically, the techniques for expeditiously setting up multimedia calls in IP-based mobile networks have yet to be incorporated in the aforementioned Protocol. It is these details to which the present invention is directed.